Download 11 Chap 17 annelida

Phylum Annelida
Segmented Worms
Metameres in Polychaeta
metamere = segment, or repeating body unit
Metameric Organs and Systems
– Coelom
– Nerves and ganglia
– Metanephridia
• paired excretory and osmoregulatory
organs
– Blood capillaries
• of the closed circulatory system
– Parapodia
Classification of Annelida
• c. Polychaeta bristle worms
• c. Clitellata
– sc. Oligochaeta earthworms
– sc. Hirudinea leeches
Class Polychaeta
“many chaetae”
– also called setae
• complex head appendages and parapodia
– fit them for many feeding niches
• important members of marine benthos
– deposit-feeders, filter-feeders, carnivores
Polychaete Anatomy
Hickman Fig. 10-2
(jaws protruding)
prostomium
parapods
Polychaete Diversity
Hickman Fig. 10-3A, 10-4, 10-10
surface depositfeeder
lug worm
(deposit
-feeder)
paper tube worm
(filter-feeder)
sand worm
(carnivore)
Trochophore Larva
• Present in many marine Polychaeta
– same as Mollusca and other phyla
• [Clitellata have direct development]
. . . egg to juvenile with no larva
Oligochaeta - “few chaetae”
a subclass of Clitellata
• many terrestrial and freshwater but few
marine species
– mostly thread-sized
– mostly deposit-feeders
• which mainly digest bacteria
• a few are grazers or carnivores
• freshwater species composition indicates
water quality
Earthworm
Anatomy
Campbell Fig
33.23
Hermaphroditic Oligochaete
Hickman Fig. 10-11 A
Monecious
Clitellum Function
compare Hickman Fig. 10-15
• guides sperm
transfer in
mating
• forms cocoon
for eggs
Metamere features
Hirudinea
another subclass of Clitellata
•
•
•
•
•
anterior and posterior suckers
expandable intestinal caeca
no chaetae or internal septa
hermaphrodites
clitellum visible only during egg-laying
Leech Anatomy
Hickman Fig. 10-18B
Leech Biology
• nearly all freshwater
• many are carnivores, not parasites
• produce anesthetics, anti-clotting enzymes,
and antiseptics
• larger blood-suckers have medical uses
– relieve excessive swelling and blood pressure
near tissue grafts